The bone marrow aspirate smear shows hypercellularity with a predominance of granulocytic proliferation that is similar to the peripheral blood. There is minimal dysplasia in the myeloid lineages (granulocytic, erythroid, and megakaryocytic). The percentage of blasts is less than 5% of the total bone marrow nucleated cells. If the blasts reach 20% or more, it indicates progression to blast crisis.
The bone marrow megakaryocytes may be smaller than normal and, in this case, are called micromegakaryocytes, as seen in the image to the right. They may be normal or increased in number.
